The present invention relates to a thermoplastic aromatic polycarbonate molded article which has improved weatherability and improved resistance to coloring. More particularly, it relates to a coextruded polycarbonate resin article having improved weatherability and improved coloring resistance which comprises a thermoplastic aromatic polycarbonate resin core layer having on at least one side thereof a thermoplastic aromatic polycarbonate resin cover layer containing a triazine light stabilizer and is useful as various molded articles such as food packaging containers, interior and exterior automotive trim parts, and precision machines, films, constructional materials, and the like.
Polycarbonate resins are widely used as windowpanes, roofing materials for arcades, food packaging containers, automotive parts, precision machines, etc. for their strength, rigidity, wear resistance, chemical resistance, and transparency.
However, polycarbonate resins have limited applicability because they have insufficient weatherability and are prone to discoloration or strength reduction when used outdoors or under fluorescent lamps.
Hence, polycarbonate resins have been used in combination with one or more than one of various light stabilizers. In particular, benzotriazole light stabilizers are in general use because of their relatively high effects. Benzotriazole light stabilizers are effective to some extent but still insufficient for imparting resistance to coloring by high-temperature processing, leaving room for further improvement.
Further, polycarbonate resins easily receive damage to the surface by intense ultraviolet radiation, developing a great number of fine crazes on the essentially glossy surface, which results in haze.
Polycarbonate resin molded articles having a core layer on which a light stabilizer-containing cover layer is provided by coextrusion to protect the surface have been proposed as disclosed, e.g., in Japanese Patent Laid-Open No. 101360/84, but they are disadvantageous in that the resin is colored. Japanese Patent Laid-Open No. 165419/89 discloses a polycarbonate resin coextruded article having a cover layer containing a benzotriazole light stabilizer. This technique involves the problem that the resin is colored when processed at an extremely high temperature of 300.degree. C. or higher with a large amount of the light stabilizer compounded therein. British Patent 2290745 describes a polycarbonate resin coextruded article having a cover layer containing a triazine light stabilizer. However, sufficient weatherability is not obtained due to poor compatibility of the light stabilizer with the resin component.